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[Objective] Compared with conventional gas fuel, hydrogen is more susceptible to explosion. Meanwhile, the existence of obstacles notably stimulates hydrogen combustion and accelerates flame propagation, causing more serious consequences of accidents. To reduce destructive damage caused by hydrogen combustion under obstacle conditions, it is particularly important to reveal the influences of different obstacle conditions on the characteristics of flame propagation of hydrogen. [Methods] Based on large eddy simulation, the hydrogen/air combustion and explosion processes under different obstacle shapes and blockage rate conditions were numerically simulated.Focus was given to the research on different flame propagation velocities caused by different obstacle shapes and the sensitivity to blockage rate changes. [Results] Under low blockage rate, grid-type obstacles had a stronger destructive effect on the regular flow field at the flame front than single-side obstacles, and as the number of voids in grid-type obstacles increased, their destructive effect on the flow field motion further intensified, making it difficult for the flame front to recover to a regular state. When the blockage rate went up, the difference of the shapes of obstacles became insignificant in causing damage to the regular flow field, and the flame front was continuously distorted under all obstacle conditions. As the blockage rate continued to increase, single-side obstacles brought higher peak flame propagation velocity than grid-type obstacles. At the same blockage rate, the mechanism of flame acceleration by grid-type obstacles can be changed by adjusting the single void area to enhance the acceleration effect. [Conclusion] The shape and blockage rate of obstacles are the key factors influencing the state of flame front behind obstacles.The single-side obstacle is more sensitive to the blockage rate,while the grid-type obstacle has higher acceleration potential.The research results provide basic reference data for the prevention and control of hydrogen fire accidents and serve as a reference for the design of hydrogen power systems.

Background In recent years, medically unexplained physical symptoms (MUPS) are widely concerned by domestic and foreign scholars. However, China started late in this field with relatively backward development. It is of significant importance for the promotion of MUPS field development in China to learn the researches on MUPS by international scholars. Objective To discusses the current status, research hotspots and development trends of MUPS internationally by using bibliometrics method. Methods The papers related to MUPS from inception to 2022-08-15 were searched based on Web of Science core collection databases from July to August in 2022. The bibliometric analysis was performed on the included papers in terms of publication volume trends and the distributions of authors, institutions and research areas after screening and data processing. CiteSpace 6.1R3 software was used to conduct visualization analysis on collaboration between countries or regions, document co-citation, keywords co-occurrence, keywords clustering, and keywords with bursts. Results A total of 1 615 papers were finally included, the number of annual publications in studies regarding MUPS showed an overall upward trend from 1985 to 2022, with the most rapid growth from 2014 to 2016. ROSMALEN J G M (43 papers), WITTHOFT M (41 papers) and RIEF W (31 papers) ranked the top three authors in terms of number of publications, and the total citations of the three scholars' papers also ranks in the top 10, with 954 times, 1 275 times and 1 339 times, respectively. The top three institutions in terms of number of publications were all from the UK, including University of London (143 papers), King's College London (95 papers) and University of Manchester (84 papers). The top three countries/regions in terms of number of publications were England (422 papers), the United States (341 papers), and Netherlands (268 papers), all of which cooperated closely with other countries. A total of 75 research areas were involved in all the literature, with most studies in psychiatry (605 papers). The literature co-citation network map includes 1 393 nodes and 6 108 connections, and the paper with the highest co-citation frequency was titled Somatoform Disorders and Medically Unexplained Symptoms in Primary Care. Except of "Medically unexplained symptoms", the top five keywords in terms of occurrence frequency were "primary care" (422 times), "somatoform disorder" (405 times), "somatization" (354 times), "prevalence" (217 times) and "depression" (211 times). A total of 12 clusters were obtained by keywords clustering analysis, reflecting in the subject category and epidemiological characteristics of MUPS, key subtypes of MUPS, main treatment methods and management of MUPS. Keyword with the highest intensity of burst was "somatic symptom disorder" "children" "bodily distress syndrome" "somatic symptom disorder" and "model" have burst in recent years and persisted till now. Conclusion At present, the publications of international studies regarding to MUPS show an upward stage, with research hotspots and trends mainly focus on the sutypes of MUPS with more researches, attention to juvenile groups and creation of effective communication models, correct evaluation and long-term management of MUPS, effectiveness of cognitive behavioral therapy for MUPS.

Flexible strain sensors from biaxially stretched carbon nanotubes (CNTs)/polydimethylsiloxane (PDMS) nanocomposites are fabricated in this study. It is shown that biaxial stretching promotes the homogeneous distribution and alignment of CNTs in the stretching plane, improving the sensing performance of the strain sensors. The optimized stretching ratios (SRs) of CNT/PDMS nanocomposites are determined. Compared to an unstretched CNT/PDMS-1.0 sensor (gauge factor [GF] value = 0.73, detectable range from 0 to 60%), the 1.5 wt% CNT/PDMS-1.5 sensor (SR = 1.5) exhibits enhanced strain sensitivity (GF = 2.8), a wider detectable range (0-370%) and better performance stability. The GF values of CNT/PDMS-2.0 and CNT/PDMS-2.5 sensors with SRs of 2.0 and 2.5, respectively, were 1.18 and 1.06, respectively, due to more significant conductive network reconstruction in the process of applying strain, leading to a decreasing GF. The possibility of sensors in the application of wearable electronic components is also demonstrated. The sensor shows a clear and stable signal output when different strain modes are applied, such as tensile, compressive, bending, and twisting. KEYWORDS CNTs, flexible strain sensor, PDMS, simultaneous biaxial stretching, orcid.org/0000-0002-8714-6576 orcid.org/0000-0001-7355-8759 orcid.org/0000-0002-1148-777X orcid.org/0000-0001-6106-1868 1 | INTRODUCTION With the development of new materials and the great progress of manufacturing technology, flexible and stretchable electronic products, such as stretchable conductors, transistors, [...]

The combination of a high sensitivity and a wide strain detection range in conductive polymer composites-based flexible strain sensors is still challenging to achieve. Herein, a double-percolation structural fiber strain sensor based on carbon nanotubes (CNT)/styrene butadiene styrene (SBS)@thermoplastic polyurethane (TPU) composite was fabricated by a simple melt mixing and fused filament fabrication strategy, in which the CNT/SBS and TPU were the conductive and insulating phases, respectively. Compared with the sensor without the double percolated structure, the CNT/SBS@TPU sensor achieved a lower percolation threshold (from 2.0 to 0.5 wt%, a reduction of 75%), and better electrical and sensing performance. It is shown that the strain detection range of the CNT/SBS@TPU sensor increases with increasing CNT loading. An opposite trend was observed for the sensitivity. The 1%-CNT/SBS@TPU sensor exhibited a high conductivity (1.08 * [10.sup.-3] S/m), high sensitivity (gauge factor of 2.65 [10.sup.6] at 92% strain), wide strain detection range (0.2%-92% strain), high degree of linearity ([R.sup.2] = 0.954 at 0-10% strain), broad monitoring frequencies (0.05-0.5 Hz), and excellent stability (2000 cycles). Moreover, the CNT/SBS@TPU sensor was shown to successfully monitor a range of human physiological activities and to be capable of tactile perception and weight distribution sensing. KEYWORDS double percolated structure, fiber strain sensor, nanocomposites, styrene butadiene styrene, thermoplastic polyurethane, 1 | INTRODUCTION In recent years, conductive polymer composites (CPCs) composed of elastic matrix materials and conductive nanofillers have been rapidly developed and are widely used in various applications including [...]